There are various environments such as large buildings or industrial works, docks, mines, airports, railways, tunnels and so forth where communication between a base station and mobile vehicles or personnel (`mobiles`) or between two mobiles is necessary. Full radio communication using significant power broadcasting presents problems in some environments due to potential hazard and in others, in terms of channel availability and regulatory conditions. More serious difficulties are encountered when wideband signals such as video signals are to be transmitted; and are aggravated by changes in geometry. It is known to provide distributed low power transmission from or reception by a leaky feeder cable which extends from a base station. A leaky feeder cable of the known type comprises a coaxial cable which has deliberately imperfect screening.
One problem that arises in a variety of circumstances is a need to shield the feeder physically while permitting propagation in the manner of a leaky feeder and particularly to enable servicing of the feeder for very long periods of time.